1. Field of the Invention
The present invention relates to a motor provided with a sensor magnet at an end portion of a shaft.
2. Description of the Related Art
A contactless rotation angle detection device for detecting, e.g., the rotation angle of a motor, is usually of the type using, e.g., a resolver or a plurality of Hall ICs.
In recent years, a rotary encoder including a magnet attached to an end surface of a shaft and a sensor provided in an opposing relationship with the magnet has been used.
Japanese Patent No. 3517350 discloses a conventional example of a motor in which a magnet attached to a rotating shaft is prevented from moving about the rotating shaft through the use of a bush.
However, if the magnet includes a raised portion or a recess portion formed in the magnet that is used to restrict movement of the magnet about the rotation axis of a shaft, the magnet becomes, e.g., difficult to mold and vulnerable to cracking or breakage. This vulnerability is disadvantageous in terms of productivity and durability. Moreover, raised portions and recessed portions may cause a change in the magnetic force of the magnet, thereby adversely affecting the detection accuracy of a sensor including the magnet.